From: Chuck Harris <[EMAIL PROTECTED]> Subject: Re: [time-nuts] Re: Accuracy of a sound card Date: Tue, 23 Aug 2005 15:43:54 -0400 Message-ID: <[EMAIL PROTECTED]>
> Hi Poul, Hi Chuck, > I am quite aware that making a soundcard more accurate is gilding the > lilly. > > But if you return to the middle of this thread, where I offered powerline > noise up as a reasonably accurate, ubiquitious timing reference, and had > my suggestion refuted by a gentleman with a soundcard based spectrum > analyzer, you would understand my point. > > If you are going to use a soundcard as the basis for a spectrum analyzer, > and you are going to let your software readout 5 or 6 significant digits, > you are going to have to also realize that the oscillator in the sound card > is not very good, and your data is suspicious. > > In an effort to illustrate this point, TVB made a graph of the characteristics > of his high quality sound card, and low and behold, it behaves just like it > has an > uncompensated crystal oscillator...imagine! Like expected, indeed. Frequency accuracy and stability does not magically apear from thin air (but you can get a fair sense of it from space with magicless GPS for instance) in an el-cheapo solution. > There are no adjustments of any kind on these boards, let alone any for > frequency. There is no reason to believe that they will be any more accurate > than musicality requires. If you don't have a sampling clock input of any kind, modding one in should be considered unless a audio-card upgrade is over the horizon. Having it lock to a 10 MHz (or other similar frequency) source of sufficient longterm stability and frequency accuracy should be of interest. Cheers, Magnus _______________________________________________ time-nuts mailing list [email protected] https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
